What is the area of a regular pentagon with a side length of 9 millimeters and an apothem length of 6.2 millimeters?

The area of a regular polygon is equal to half of the product of its apothem and perimeter.

A = 0.5aP

Find first the perimeter,

P = 5 x (9 mm)

P = 45 mm

Substituting the perimeter and the apothem to the first equation,

A = 0.5 (45 mm) (6.2 mm)

A = 139.5 mm²

Therefore, the area of the regular pentagon is equal to 139.5 mm².